BACKGROUND:The placenta is recognized as an endocrine organ,largely due to its secretions of steroid hormones,including progesterone,androgens,and estrogens.Steroid hormones play an essential role in the progression of pregnancy,fetal development,and growth.Furthermore,steroids are necessary for establishment and maintenance of a normal pregnancy,preparing the endometrium for implantation,stimulating endometrial secretions,and regulating uterine blood flow,however the exact mechanism of sex steroid signaling through their receptors in placental function is unknown.OBJECTIVE:In this review,we will provide an overview of the current knowledge on sex steroid receptors in normal placental development,as well as evidence of abnormal signaling associated with placental dysfunction.METHODS:A systematic literature search was performed using the NCBI PubMed search engine,including the following key works:estrogen receptor,androgen receptor,placenta,placental development,cytotrophoblast,and differentiation.RESULTS:Of the over 700 articles that were retued,125 studies focused on estrogen and androgen receptors in human placenta development and function during normal and abnormal pregnancy,as well as in rodents and ruminants placentae.CONCLUSION:Receptors for both estrogens and androgens have been localized within the mammalian placenta,but surprisingly little is known about their signaling in trophoblast cell differentiation and function.An emerging picture is developing in which estrogen receptors possibly play role in cytotrophoblast proliferation and extravillous trophoblast invasion,whereas androgen receptors are involved in syncytiotrophoblast differentiation and function.